The objective of this research is to do a genetic study of geotactic and phototactic behavior in various species of Drosophila using Hirsch-Hadler mazes as classification instruments. In addition to investigating the importance of polygenes for these types of behavior, experiments will be designed to determine whether differences exist among species in their ability to discern various types of light, the influence, if any, of certain environmental factors, the importance of single mutant genes in Drosophila melanogaster, and how the responsible genetic mechanisms relate to the phenomenon of genetic homeostasis.